1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine mounted to an automotive vehicle such as a passenger car or a truck, for example, and to a method for manufacturing the alternator.
2. Description of the Related Art
FIG. 29 is a perspective of a stator of a conventional automotive alternator such as described in Japanese Patent No. 2927288, for example, FIG. 30 is a perspective showing a conductor segment used in the stator in FIG. 29, and FIGS. 31 and 32 are perspectives from a front end and a rear end, respectively, of part of the stator in FIG. 29.
This stator 300 includes: a stator core 301; a stator winding 302 wound onto the stator core 301; and insulating members 304 mounted inside slots 303, the insulating members 304 electrically insulating the stator winding 302 from the stator core 301. The stator core 301 is a cylindrical laminated core laminated by stacking thin steel plates which are plate-shaped magnetic members, and has a number of slots 303 extending axially disposed at even pitch circumferentially so as to be open on an inner circumferential side. The stator winding 302 is constructed by joining a number of short conductor segments 305 in a predetermined winding pattern.
In the stator 300 of an automotive alternator having the above construction, because the stator winding 302 is constructed by inserting short conductor segments 305 formed in the general U shape into the slots 303 of the stator core 301 from the rear end and joining end portions 305b of the conductor segments 305 extending outwards at the front end, the coil end groups are composed of a large number of joint portions, allowing short-circuiting accidents to occur easily because the joint portions easily short-circuit with each other.
A large number of the short conductor segments 305 must be inserted into the stator core 301 and their end portions must be joined by welding, soldering, etc., making operability significantly poor. Furthermore, the amount of each conductor segment 305 which is inserted into the slots 303 must be greater than the length of the stator core 301, facilitating damage to the insulation coatings and insulating paper and reducing the quality of the finished product. In addition, when joining the end portions, short-circuiting often occurs between the joint portions due to spilt solder or weld melt, making mass-producibility significantly poor.
In contrast to the conventional construction using conductor segments 305, Japanese Patent Laid-Open No. HEI 8-298756 discloses a stator construction consisting of a number of coil pieces formed by first winding a number of straight-angled conductors a number of times into a generally hexagonal shape and inserting the coil pieces into slots in semicircular divided core portions.
In this stator, the coil pieces are inserted into the slots of the semicircular divided core portions in order in a radially outward direction. In other words, first facing side portions of the hexagonal coil pieces are positioned in an inner circumferential layer which is a layer on the inner side of the slots, and second facing side portions are positioned in an outer circumferential layer which is a layer on the outer side a predetermined number of slots away.
In this stator, although the alignment of the coil ends extending outwards from the slots is good, when joining the divided core portions to each other, the first side portions of the coil pieces are already inserted into the slots of a first divided core portion but because it is necessary to perform the operation of inserting the coil pieces into the slots of a second divided core portion at the same time as the operation of connecting the divided core portions, a temporary holding jig or the like must be used to perform a complicated operation, making productivity significantly poor.
Furthermore, insulating members between the divided core portions and the coil pieces are not disclosed, but under these working conditions, the operation of inserting insulating members must be complicated.
Forming the stator core by joining a number of divided core portions has also been troublesome, and forming the radial dimensions, etc., of each of the divided core portions so as to be uniform has been difficult.
Japanese Patent Laid-Open No. HEI 9-103052 discloses a stator 400 in which winding groups formed in a straight shape are inserted into a straight-shaped base core in a slot depth direction and the base core is bent into a cylindrical shape in a later process in order to improve the space factor of the conductors in the slots. FIG. 33 is an overall perspective of the stator 400 manufactured by this method. Although, insertion of the winding groups is significantly improved, because the winding groups have straight bridging portions extending circumferentially between the slots 401, the alignment of coil ends 402 extending outwards from the slots 401 is significantly poor, leading to increased radial dimensions and short-circuiting between the conductors in the coil ends 402.
Furthermore, no disclosure is made concerning insulating members between the core and the winding, but since interference between the coil ends is great, deformation of the winding is great even inside the slots, and insulation between the core and the winding cannot be considered good.
In the conventional automotive alternator disclosed in Japanese Patent No. 2927288, problems have been that a large number of the short conductor segments 305 must be inserted into the stator core 301 and their end portions must be joined by welding, soldering, etc., making operations and insulation significantly poor, that insulation coatings and insulating paper have been easily damaged during insertion of the conductor segments 305 into the slots, and when joining the end portions, that short-circuiting often occurs between the joint portions due to spilt solder or weld melt, making mass-producibility significantly poor.
In the alternator of Japanese Patent Laid-Open No. HEI 8-298756, problems have been that forming the stator core by joining a number of divided core portions has been troublesome, requiring a complicated operation using a temporary holding jig, thereby making the assembly operation of the stator and the installation of the insulating members in the core poor.
In the automotive alternator disclosed in Japanese Patent Laid-Open No. HEI 9-103052, the alignment of coil ends 402 extending outwards from the slots 401 is significantly poor, leading to increased radial dimensions and short-circuiting between the conductors in the coil ends 402, and insulation between the core and the winding has been sparse even within the slots, leading to problems such as facilitation of the occurrence of short-circuiting, etc.
The present invention aims to solve the above problems and an object of the present invention is to provide an alternator significantly improving assembly and enabling insulation between the stator core and the winding to be improved, and to provide a method for manufacturing the alternator.
To this end, according to the present invention, there is provided an alternator comprising: a rotor for forming north-seeking (N) and south-seeking (S) poles alternately about a rotational circumference; and a stator comprising: a stator core surrounding the rotor; and a polyphase stator winding installed in the stator core, the stator core being formed with a number of slots extending axially at a predetermined pitch in a circumferential direction and being provided with an abutting portion extending axially, abutting portion making stator core into an annular shape by abutting end portions of the stator core, the polyphase stator winding comprising a number of winding portions in which long strands of wire are wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots, the strands of wire folding back outside the slots at axial end surfaces of the stator core, and an insulating member being interposed between the stator core and the winding.
According to another aspect of the present invention, there is provided a method for manufacturing the alternator wherein the insulating member is first disposed on the winding before the winding is inserted into the slots of the stator core.
According to still another aspect of the present invention, there is provided a method for manufacturing the alternator wherein a base insulating member is first disposed between the slots and the winding; and insulating member is interposed between said stator core and the winding by inserting the winding into said slots.